As anyone who drives a vehicle knows, the price of petroleum is rising rapidly due to increasing worldwide demand and a lack of new supply to address the increasing demand. Moreover, petroleum is a known source of greenhouse gasses that have been linked to global warming and a myriad of problems caused by global warming. That has led to a demand for alternative energy sources that can be used to power ever-increasing worldwide fleets of vehicles powered by internal combustion engines. One such alternative that is being rapidly developed is ethanol, but ethanol is made from food sources (sugar cane or corn) and that will rapidly compete with the need for such food sources for human and animal feed. Moreover, in the U.S. ethanol is not cost effective and requires a large government subsidy for utilization to make ethanol from corn. Clearly, ethanol is not a long-term solution.
Other avenues have been explored in what is referred to as “biodiesel” which is really methylesters from various plant oils that is required to be mixed with diesel fuel from traditional petroleum sources. Biodiesel requires plant oils as a starting material and is synthesized in an energy-intensive process that generates glycerol as a by-product. Some biodiesel has utilized waste cooking fats or used plant oil triglycerides as starting materials, but the synthesis process is more difficult due to the contamination of the used oils. But there are not enough such waste products in existence to be a realistic source for transportation needs.
Hydrogen has been considered an important long-term solution to the energy crisis of growing demand and dwindling supply due to the ability to generate hydrogen from renewable sources of energy (e.g., electricity such as wind power or hydropower) and the fact that the combustion product is water vapor. Hydrogen can be generated using known techniques by electrolysis of water or oxidation of other gasses such as methane or ammonia. Water electrolysis, in particular, is an attractive means for generating hydrogen gas. This is particularly important, as there is a growing capacity of wind-powered electricity generation. However, most wind blows at night when the electricity demand is the lowest (due to less need to drive air conditioning and the like). Therefore, if there is a reliable means for storing hydrogen, such stored hydrogen can serve as a means for storing excess electricity generated to be used for either transportation fuel or for generating electricity using a fuel cell. Right now it is estimated that up to 45% of electricity that is generated is wasted due to lack of demand when such electricity is generated. Therefore, there is a need in the art to be able to store and transport hydrogen with the ability to release the stored hydrogen on demand.
Hydrogen gas can be stored as a compressed gas or as a cryogenic liquid. Both methods are problematic. Storing hydrogen, as a gas requires large, heavy and thick storage vessels because hydrogen gas is less dense in terms of volume of storage for the weight of hydrogen gas stored. Moreover, when used for any transportation applications, such as a vehicle, the problem of a hydrogen gas storage tank is one of excessive weight and volume needed to power a vehicle for anything except a short distance (using a hydrogen internal combustion engine). The largest risk and drawback to a hydrogen tank in a moving application (such as a vehicle for either gas storage or cryogenic liquid storage) is that in any severe crash or even in the case of a terrorist attack, the presence of a hydrogen storage tank that is breached can unleash an excessively large explosion that can cause widespread and potentially catastrophic damage far beyond any other fuel or other improvised explosive device. Hydrogen powered vehicles using a hydrogen gas or cryogenic liquid storage tank would become the vehicle of choice for terrorist suicide or remote-controlled bombers. Further, cryogenic storage of hydrogen in a tank losses several percent of the stored hydrogen per day, leading to empty tanks whenever such a vehicle is left idle for a period of time (such as long term parking lots). Therefore, there is a need in the art to develop hydrogen storage and release technologies that avoid storing hydrogen in a gaseous or cryogenic liquid state.
Hydrogen storage technologies using larger molecules than H2 have generally been developed into two basic means. Metal or chemical hydrides have been developed to store and release hydrogen. However, such hydrides are generally in more of a solid state of matter that do not lend themselves to fuel applications, particularly when trying to adopt existing fuel (petroleum) infrastructure to a newer hydrogen fuel applications. Moreover, such metal hydrides can be dehydrogenated but often cannot be recycled or rehydrogenated. Therefore, the application of metal or chemical hydrides will not be for transportation on a wide scale basis because they will cause massive environmental issues due to the need to dispose of dehydrogenated hydrides.
Spent forms of recyclable liquid fuels that release hydrogen gas, include aromatic compounds such as benzene and naphthlene (aromatic substrates) that undergo reversible hydrogenation to form cyclohexane and decalin, respectively. U.S. Pat. No. 6,074,447, for example, describes dehydrogenating methylcyclohexane, decalin, dicyclohexyl, and cyclohexane to toluene, naphthalene, biphenyl and benzene, respectively in the presence of an iridium catalyst at temperatures of 190° C. or higher. Yet even at such temperatures, hydrogen release reactions require several minutes for full release and often exist as solids at room temperatures. When one pushes on an accelerator petal to power a vehicle forward, it would be highly problematic in today's traffic to have to wait a minute or two before hydrogen fuel is release to the engine, yet a buffer system, if employed has all of the problems of storing gaseous hydrogen. Therefore, the requirement of immediate and complete dehydrogenation is a necessary and required characteristic of hydrogen fuel for any transportation application. The present disclosure addresses the need for immediate and complete release of all moles of hydrogen from such a fuel.
Liquid fuels have the advantage that they can be transported using existing petroleum infrastructure (e.g., pipelines and tankers, something ethanol cannot do) and often can be recycled or re-hydrogenated to avoid an environmental crisis if used in the field of transportation. There is an ongoing effort to develop and commercialize both internal combustion engines that utilize hydrogen as a fuel and fuel cells that also utilize hydrogen as a fuel. Both applications generate water upon combustion of the hydrogen gas with oxygen from the atmosphere. However, widespread use of such energy solutions requires better methods for storing, transporting and releasing hydrogen gas upon demand.
One form of hydrogen fuel for release, storage and recycling of hydrogen fuels uses a sulfur-containing heteroatom that is cyclized on dehygrogenation and when re-hydrogenated the ring is broken to form a linear, thiol-containing alkane moiety.
The use of ablation patterning of various polymeric materials, such as, polyimides, is disclosed in U.S. Pat. No. 4,508,749. This discloses, for example, a use of ultraviolet (U.V.) radiation for etching through a polyimide layer. Electrical connections are then made through the openings to the metal layer. U.S. Pat. No. 5,236,551 likewise discloses ablation etching for patterning a polymeric material layer which is then used as an etch mask for etch patterning, using wet or chemical etchants, an underlying layer of metal.
In a typical ablation process, a beam of laser energy is directed against an exposed surface of a body to be ablated. The laser energy is absorbed by the material and, as a result of photochemical, thermal and other effects, localized explosions of the material occur, driving away, for each explosion, tiny fragments of the material. The process requires that significant amounts of energy be both absorbed and retained within small volumes of the material until sufficient energy is accumulated in each small volume to exceed a threshold energy density at which explosions occur.
Polyimides are used in the process because such materials have a high absorptivity for U.V. light while having a relatively low thermal diffusivity for limiting the spread of the absorbed energy away from the volume where the energy was absorbed. When an excimer laser is used, because of the unique optical focusing requirements of the excimer laser it is important to the manufacturing process that the material to be ablated be flat, with a typical peak-to peak roughness of less than about 20 microns, for a given ablation operation.